Friendship could be the main reason. Naruto is a well - liked figure in the village, and Ino might simply want to spend some time with him. Just like how friends often visit each other's places.
In the fanfiction, Ino could be going to Naruto's apartments to ask for his help. Maybe there's a problem in her family's flower shop that requires Naruto's unique skills or connections. It could also be that she's planning a surprise party for Sakura and needs Naruto's place to set it up secretly.
Maybe Naruto senses that the seal is causing Anko pain or holding her back in some way. He has a strong sense of justice and helping those in need, so he decides to take action.
Well, they could also change their own relationships. Maybe Naruto wouldn't be so alone as a child, and Ino could become a stronger ninja earlier. They might train together in ways they didn't before, using the knowledge of future jutsu and strategies. They could also influence the relationships between different ninja clans, like improving the relations between the Uzumaki and the Yamanaka clans.
He could be motivated by curiosity. Naruto is always eager to learn new things and the ANBU is a mysterious organization. He might want to know what goes on in there.
It could be the same antagonists as in the original Naruto series at first, like the Akatsuki. But if Naruto and Ino change things, new antagonists might emerge. Maybe some ninja who were once allies turn against them because they fear the changes Naruto and Ino are making to the ninja world order.
Well, it could be that they have different demands that aren't being met. Maybe it's related to their missions or the way they're treated. There could be a lot of reasons!
They would probably have a very close relationship. Twins often have a special bond, so Naruto and Ino would likely be no different. They would support each other in their ninja training and missions. Ino might be a bit bossy towards Naruto, but it would be out of love. Naruto, on the other hand, would be very protective of Ino.
Well, it could be about Ino having a huge admiration for Naruto. Maybe it shows her fangirl moments like always cheering for him during battles, getting flustered when he's around, and daydreaming about him. It might also explore how this fangirl - like behavior affects her relationships with others in the Naruto universe.
I'm not really sure as this sounds like a very unethical and inappropriate concept for a fanfiction. Fanfictions should promote positive and healthy relationships, not slavery themes.
One possible fanfiction could be where Ino, with her mind - related jutsu, teams up with someone who has the Sharingan. They could go on a mission together and the Sharingan user might help Ino enhance her perception abilities. For example, if Naruto somehow had the Sharingan (in this fanfic concept), he and Ino could face an enemy that uses illusions. Naruto's Sharingan would see through the illusions and Ino could then use her mind - control jutsu on the real enemy.